Method and apparatus for manufacturing wound tube bundles

ABSTRACT

A method and an apparatus for making tube bundles for various medical applications such as oxygenators, dialyzers, and heat exchangers is described. The tube bundle is suitable for use as a heat exchanger in, for example, a blood cardioplegia circuit. The winding apparatus axially winds a flexible tube around a winding core. The apparatus includes a tube shuttle, a shuttle driver and a core driver. The core driver rotates the winding core to distribute the tube on the winding core in layers.

FIELD OF THE INVENTION

The invention relates to a method and apparatus for manufacturing woundtube bundles. More particularly, the invention is directed to themanufacture of a tube bundle for a blood cardioplegia delivery device.

BACKGROUND OF THE INVENTION

The use of hollow fiber bundles as mass transfer devices and energytransfer devices in the field of medical technology is well-known. Forexample, wound hollow fiber bundles have been used as blood oxygenatorsand dialyzers. The typical winding pattern for hollow fiber bundles canbe described as a helical wind, where the tubes are wrapped around arotating cylinder. One such winding technique is described in U.S. Pat.No. 4,975,247 by Badolato et al., which describes the means by which towind a hollow fiber oxygenator with specialized winding equipment.Badolato et al. describes winding a single fiber or fiber ribbon onto arotating core using a fiber guide which reciprocates along a lineparallel to the axis of the core. The fiber guide deposits the tubespirally around the core as the fiber guide reciprocates and the corerotates.

Typical winding techniques such as that described in the Badolato patentare limited to large, for example, 2.0 inch diameter cores. If the coreis smaller, the fiber will slide off of the core as the tubing is wound.If the core has a 2.0 inch or larger diameter, contact surface frictionwill maintain the fiber in place as the fiber is wound. Unfortunately,the relatively large diameter results in a larger priming volume whichis undesirable for most medical applications. The increased primingvolume results in increased levels of hemodilution which can bedeleterious to the patient. In certain instances, the increased primingvolume can prohibit the use of the device on smaller adults andchildren.

Alternatively, hollow fiber bundles may be wound with fiber mats whichare not subject to the winding problems of fibers or fiber ribbons,discussed above. Specifically, neither core diameter nor the specificangle at which fibers must be wound around the core to maintain thefiber's position relative to the central axis of the core are factorswhen using woven fiber mats. As a matter of fact, when a fiber bundle ismade using a fiber mat the bundle can be formed around a core with arelatively small diameter and the fibers can be substantially parallelto the axis of the core. However, fiber mats are expensive because ofthe additional complexities of the weaving process. Further, weavingtypically precludes the direct cost control over the manufacturingprocess that exists when a bundle is wound from a single fiber or fiberribbon. Therefore, it would be desirable to have a winding technique andapparatus which combines low cost, low prime volume and direct controlover production without the disadvantages associated with presentwinding techniques or wound fiber mat device designs.

SUMMARY OF THE INVENTION

In one aspect, the invention is an apparatus for manufacturing a woundtube bundle for use in medical device applications. The apparatusincludes a tube, a tube shuttle, a winding core, a shuttle driver, and acore driver. The tube shuttle is shaped to receive and distribute thetube around the winding core. The winding core has a body, a firstwinding disk and a second winding disk. The first winding disk isattached to a first end of the body and the second winding disk isattached to a second end of the body. The first winding disk and thesecond winding disk are shaped to accept tube from the tube shuttle. Theshuttle driver and core driver are configured to rotate the shuttle andthe winding core to distribute the tube on the winding core in layers.Each layer has a plurality of rows wound onto and distributed around thecore. Each row is substantially parallel to the other rows and is alsosubstantially parallel to the longitudinal axis of the core. The shuttledriver rotates the tube shuttle about a shuttle axis in a circularwinding motion to wind tube onto the core. The core driver incrementallyrotates the winding core about a longitudinal axis of the core, thelongitudinal axis being substantially perpendicular to and substantiallyintersecting the shuttle axis. The core driver can be configured toincrementally rotate the winding core one increment after each fullrotation of the tube shuttle around the winding core. The apparatus canalso include a computer control to control the tube shuttle and windingcore. The computer control is preferably configured to regulate at leastone of the rate, degree and timing of the rotation.

The apparatus can also include a tube bobbin for holding a length of thetube and for dispensing the tube to the tube shuttle. The bobbin can beconnected to a bobbin driver. The bobbin driver incrementally rotatesthe tube bobbin. The bobbin driver can be connected to a computercontrol. The computer control regulates the rotation of the bobbin.Preferably, the computer control regulates at least one of the rate,degree and timing.

The apparatus can also include a means for providing a constant tensionto the tube as the tube is unwound from the bobbin.

The winding disks can also have a plurality of fins extending radiallyfrom a peripheral edge of the first and second winding disks. Theplurality of fins define a plurality of primary notches. The primarynotches are configured to accept tube and hold the tube in position asit is wound onto the winding core. The plurality of fins can also definea plurality of secondary notches. The secondary notches are shaped toreceive tube from the tube shuttle. The primary and secondary notcheseach have a length measured from the fin's peripheral edge towards thecentral axis. The length of the primary notches is greater than thelength of the secondary notches. The plurality of fins can also define aplurality of tertiary notches shaped to receive tube from the tubeshuttle. The length of the tertiary notches being less than the lengthof the primary and secondary notches.

The winding core can also have cutting pads to better facilitate windingand cutting. The cutting pads are positioned such that a first cuttingpad is attached opposite the body on the first winding disk and a secondcutting pad is attached opposite the body on the second winding disk.

In a second aspect, the invention is an apparatus for manufacturing awound tube bundle for use in medical device applications. The apparatusincludes a tube and a tube shuttle, as described above, and a windingcore. The winding core has a body, a first winding disk attached to afirst end of the body and a second winding disk attached to a second endof the body. The first and second winding disks have a peripheral edgeand a central axis that substantially coincides with a longitudinal axisof the winding core. The first and second winding disks further have aplurality of fins extending from the peripheral edge towards the centralaxis. The fins define a plurality of primary notches shaped to receivetube from the tube shuttle. The fins can further define a plurality ofsecondary notches shaped to receive tube from the tube shuttle. Theprimary and secondary notches each have a length as measured from theperipheral edge towards the central axis. The length of the primarynotches is greater than the length of the secondary notches. The finscan still further define a plurality of tertiary notches shaped toreceive tube from the tube shuttle. The tertiary notches also have alength as measured from the peripheral edge towards the central axis.The length of the tertiary notches is less than the length of thesecondary notches.

In a third aspect, the invention is an apparatus for manufacturing awound tube bundle. The apparatus includes a tube and a tube shuttle, asdescribed above, and a winding core. The winding core has a body with afirst winding disk attached to a first end of the body and a secondwinding disk attached to a second end of the body. The first and thesecond winding disks are shaped to accept tube from the tube shuttle andhave a diameter greater than a diameter of the body. The greaterdiameter of the winding disks creates a space between the tubes and bodywhen the tube is wound onto the winding core.

In a fourth aspect, the invention is an apparatus for manufacturing awound tube bundle. The apparatus including a tube and a tube shuttle, asdescribed above, and a winding core. The winding core having a body witha first cutting pad attached to a first end of the body and a secondcutting pad attached to a second end of the body. The first and thesecond cutting pads are shaped to accept tube from the tube shuttle.

In fifth aspect, the invention is an apparatus for manufacturing a woundtube bundle. The apparatus includes a first tube, a second tube, a tubeshuttle, and a winding core. The tube shuttle is shaped to receive anddistribute the first tube and the second tube. The winding core has abody, a first winding disk and a second winding disk. The first windingdisk is attached to a first end of the body and the second winding isdisk attached at a second end of the body. The first winding disk andthe second winding disk are shaped to accept the first tube and thesecond tube from the tube shuttle.

In a sixth aspect, the invention is a winding core for use with awinding apparatus for making a wound tube bundle. The winding coreincludes a body, a first winding disk and a second winding disk. Thebody has a first end and a second end. The first winding disk isattached to the first end of the body and the second winding disk isattached to the second end of the body. The winding disks have adiameter greater than the diameter of the body.

The winding core may include a winding pin extending co-axially from thewinding core. The winding pin can function to displace tube as the tubeis wound around the core and thereby, hold the rows of tube on the coreas the wound tube forms a dome at the ends of the winding core. Thewinding pin can further be shaped to secure the winding core to thewinding apparatus.

The winding core may include a first cutting pad attached to the firstwinding disk and a second cutting pad attached to the second windingdisk.

The winding core may also include a plurality of fins extending from theperipheral edge towards the central axis, the fins defining a pluralityof primary notches shaped to receive tube. The fins can also define aplurality of secondary notches shaped to receive tube. The primary andsecondary notches each have a length as measured from the peripheraledge towards the central axis. The length of the primary notches isgreater than the length of the secondary notches. The fins can alsodefine a plurality of tertiary notches shaped to receive tube. Thetertiary notches also have a length as measured from the peripheral edgetowards the central axis. The length of the tertiary notches is lessthan the length of the secondary notches.

In seventh aspect, the invention is a method for manufacturing a woundtube bundle. The method includes providing a winding core shaped toaccept a tube, winding a row of a tube around the winding coresubstantially parallel to the longitudinal axis while the winding coreis essentially stationary, incrementally rotating the winding core, andwinding a second row of tube around the winding core while the windingcore is essentially stationary. The winding core has a body with a firstand a second end and a longitudinal axis. The winding core can furtherbe provided with a first cutting pad attached to the first end of thewinding core and a second cutting pad attached to the second end. Themethod can also include further incrementally rotating the core andwinding rows of tube sequentially until a desired number of rows arewound around the winding core.

The method can also include fitting the wound bundle into a housingshaped to accept the bundle. Once fitted within the housing, the methodcan include sealing the first and second ends of the wound bundle withinthe housing using a potting material. The potting material can be apolyurethane. Once potted, the method can include cutting the ends ofthe bundle through the cutting pad to expose the lumen within the tubes.Once the bundle is cut, the method can include attaching a first end capover the first end of the housing and a second end cap over the secondend of the housing such that the end caps communicate with the lumen ofthe tubes.

In an eighth aspect, the invention is a method for manufacturing a woundtube bundle. The method including providing a winding core, winding arow of a tube around the winding core such that the tube is receivedwithin primary notches of first and second winding disks, rotating thewinding core, and winding a second row of tube around the winding coresuch that the tube is received within primary notches of the first andsecond winding disks. The winding core including a body, the firstwinding disk attached to a first end of the body and the second windingdisk attached to a second end of the body. The first and second windingdisks have a peripheral edge and a central axis that substantiallycoincides with a longitudinal axis of the winding core. The first andsecond winding disks also have a plurality of fins extending from theperipheral edge towards the central axis the fins defining the pluralityof primary notches. The primary notches are shaped to receive tube.

In a ninth aspect, the invention is a method for manufacturing a woundtube bundle. The method including providing a winding core, winding arow of a tube from a first winding disk to a second winding disk aroundthe winding core, rotating the winding core, and winding a second row oftube from the first winding disk to the second winding disk around thewinding core. The winding core having a body with the first winding diskattached to a first end of the body and the second winding disk attachedto a second end. The first winding disk and the second winding disk areshaped to accept tube and have a diameter greater than a diameter of thebody.

In a tenth aspect, the invention is a method for manufacturing atransfer device. The method including providing a winding core, windinga row of a tube from a first cutting pad to a second cutting pad aroundthe winding core, rotating the winding core, and winding a second row oftube from the first cutting pad to the second cutting pad around thewinding core. The winding core having a body, the first cutting padattached to a first end of the body and the second cutting pad attachedto a second end of the body. The first cutting pad and the secondcutting pad are shaped to receive tube.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an embodiment of winding apparatusaccording to the present invention.

FIG. 2 is a isometric view of an embodiment of the winding core.

FIG. 3 is a cross-sectional view of the unfinned winding disk of anembodiment of the winding core with tubes.

FIG. 4 is an end view of the finned winding disk of an embodiment of thewinding core.

FIG. 5 and FIG. 6 are end views of winding disks showing alternative findesigns.

FIG. 7 is a schematic diagram of an embodiment of a computer controlledwinding apparatus in accordance with the present invention.

FIGS. 8A and 8B are a side view and a top view, respectively, of anembodiment of a bobbin tension means.

FIGS. 9A, 9B and 9C are a top views illustrating consecutive windingpatterns of the tubes as they are wound about a winding core havingwinding disks as shown in FIG. 5.

FIG. 10 is a schematic diagram of an alternative embodiment of thewinding apparatus having two bobbins.

FIG. 11 is an exploded diagram of a heat exchange device having a woundtubular bundle manufactured in accordance with the present invention.

FIG. 12 is a cross section of an embodiment of the centrifuge rotor usedduring potting of the tube bundles.

FIGS. 13A and 13B are side views of a winding core with tube and withouttube, respectively.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The method and winding device of the present invention can be used tomake hollow tube or tube bundles for various medical applications whichutilize a mass transfer device or an energy transfer device. The term“transfer device”, as used herein, is meant to be inclusive of masstransfer and energy transfer applications. These applications includebut are not limited to blood oxygenators, dialyzers, and heatexchangers. The term “tube”, as used herein, is meant to be inclusive ofall tubing, hollow fiber, or other flexible conduit known to thoseskilled in the art. The tube bundle formed in the described embodimentis suitable for use as a heat exchanger in a blood cardioplegia circuitand the dimensions, tubing, surface area, and other particulars providedin the specification are suitable therefore. The use of this method forconstructing a tube bundle for other applications may involve the use oftubes having different dimensions, specifications and materials but thebasic principles are the same.

The apparatus and method for manufacturing a tube bundle of the presentinvention can be understood generally by reference to FIG. 1. FIG. 1shows a winding apparatus designated generally as 1. Winding apparatus 1axially winds a flexible tube 30 around a winding core 10. The windingapparatus includes: a winding core 10 to accept tube 30, a core rotatingmeans 20 for rotating core 10 in the direction of arrow 21, a tubebobbin 22 from which tube 30 is drawn, a tube shuttle 26 which guidestube 30 around core 10, and a shuttle rotating means 28 which rotatestube shuttle 26 around core 10 in the direction of arrow 29.

In the finished tube bundle, tube 30 will carry a fluid within its lumenfrom one end of the tube bundle to the other end. Tube 30 may be anybiocompatible material flexible enough for winding but is typicallypolyurethane for heat exchange applications. For blood oxygenators ordialyzers tube 30 would be a hollow fiber membrane as known in the art.For a cardioplegia heat exchanger, tube 30 may have an outside diameterof 0.01 to 0.10 inches and a wall thickness of 0.001 to 0.050 inches butpreferably has an outside diameter of 0.030 to 0.045 inches and a wallthickness of 0.002 and 0.005 inches. Tube bobbin 22 holds tube 30 beforetube 30 is wound onto winding core 10. Tube bobbin 22 holds a sufficientlength of tube to continuously and completely wind core 10. Tube bobbin22 is rotatably mounted such that tube 30 can be drawn off of bobbin 22.Tube 30 can be passively drawn off bobbin 22 or can be assisted by ameans for rotating the bobbin such as a bobbin motor, shown in FIG. 7.Tube 30 is threaded from tube bobbin 22 through tube shuttle 26. Tubeshuttle 26 may be a hollow tube appropriately angled to guide the tubeas it is wound about core 10 in a manner described in more detailhereafter. The tube is then connected to winding core 10 in a mannerdiscussed in more detail hereinafter. Tube shuttle 26 is shaped so as towind tube 30 onto core 10 when tube shuttle 26 is rotated. Shuttlerotating means 28 rotates tube shuttle 26 around an axis substantiallyperpendicular to the core's axis thereby drawing tube 30 from bobbin 22and winding tube 30 onto core 10. Shuttle rotating means 28 ispreferably a stepper motor controlled by a micro-stepper drive. Tubeshuttle 26 rotates about an axis substantially perpendicular to andintersecting the core's axis. The rotation of tube shuttle 26 aroundcore 10 axially winds tube 30 onto core 10. To distribute tube 30 aroundcore 10, core 10 is rotated an incrementing angle or distance after eachrotation of the shuttle around the core. Rotation of the core by thisincrementing angle or distance aligns the periphery of core 10 to acceptanother wind of tube 30 from tube shuttle 26. Thereby, in the nextrotation, tube shuttle 26 winds a tube which is typically adjacent tothe earlier wound tube and which is substantially parallel to both theearlier wound tube and the axis of core 10. The incrementing angle usedwill depend upon the particular tube and core design used in the bundle.Core 10 is rotated by core rotating means 20 about the core'slongitudinal axis in a plane substantially perpendicular to the tubeshuttle's rotational axis. Core rotating means 20 is preferably astepper motor controlled by a micro-stepper drive.

FIG. 2 shows an embodiment of winding core 10. Winding core 10 is shapedto accept and hold tubing from the tube shuttle but is typicallycylindrical. Winding core 10 can be made from any material of sufficientstrength to withstand the stress of the winding process but ispreferably made from a rigid thermoplastic. Winding core 10 comprises abody 12 disposed between a first winding disk 14 and a secondsubstantially identical winding disk 16. The winding disks generally liewithin a plane perpendicular to the long axis of the body. The windingdisks hold the tube as it is wound around core 10. Typically, thewinding disks are circular and have a larger diameter than body 12. Fortube bundles used in cardioplegia heat exchangers, the winding diskspreferably have a diameter of greater than 1.0 inch. It is possible touse a winding disk with an outside diameter of up to about 3.0 inchesalthough for most modern medical applications this results inprohibitively high priming volumes.

As shown in FIG. 2, the winding disks can optionally have fins 17extending radially from the winding disks' outer periphery. Fins 17provide more control over the pattern of tube during winding by holdingthe rows of the tube in position during winding and potting. The addedcontrol provided by the fins allows better regulation of the bundle sizeand subsequent priming volume for specific applications. Further, theadded control contributes to improved device performance consistency andmanufacturing repeatability. The tube can be positioned with a greaterconsistency than that of the other winding processes. Each twoconsecutive fins define a notch 19 therebetween. Notches 19 guide andhold the tube in place on core 10 during winding and other manufacturingsteps as discussed hereafter. The point within a notch closest to theaxis of core 10 is the inner diameter of the notch. The point within anotch furthest from the axis of core 10 but still between two fins isthe outer diameter of the notch. The finned winding disks preferablyhave an inner notch diameter of greater than 0.25 inches and an outernotch diameter of less than 2.5 inches for winding cores used incardioplegia heat exchangers. Fins 17 are spaced so as to accept aparticular diameter of tube within the notches. The spacing between fins17 can be varied so that notches 19 will accept the appropriate sizedtube depending on the final application for the tube bundle.

During winding, creases can form as the tube bends around the windingdisks. A cutting pad 15, shown in FIG. 2, can be placed on each end ofthe core to prevent the creases from constricting the lumen of thefinished tube bundle. The cutting pads are extensions of the core whichsupport the tube as the tube is wound. The added support moves the pointat which the tubes crease outward beyond the winding disks. Thereby, thecutting pads enable the cutting of the tube beyond the constriction inthe lumen caused by the crease without having to cut below or throughthe winding disks. Cutting pads 15 can be the circular disk shape, shownin FIG. 2, or can have the same shape as the winding disk and fins, notshown. When the cutting pads have the same shape as the winding disk andfins, the cutting pads can extend along the fins a distance up to theouter notch diameter and are configured to allow the tube to fit withinthe notches. Cutting pads 15 typically extend about 0.16 inch from theend of the winding core. Pads 15 can be co-molded into the winding coreor can be bonded to the ends of the core after molding. The pad ispreferably made of a low durometer material, typically having a shorehardness of 50 A to 70 D, so as not to damage the blade during cutting.

A winding pin 18, shown in FIG. 2, extends through the end of a longaxis of body 12 protruding through first winding disk 14 and secondwinding disk 16. Winding pin 18 is shaped so as to be secured to thecore rotating means and facilitate winding. Winding pin 18 can be asingle dowel extending through core 10. Alternatively, winding pin 18can be integrally molded from the material of core 10. Winding pin 18should be formed from a material having sufficient strength to supportcore 10 during the winding process but, is typically a suitable metal orpolyurethane. Winding pin 18 can be connected to the winding apparatusby either one or both ends.

FIG. 3 shows a cross-sectional view along the outer surface of a windingdisk after winding has been completed. FIG. 3 exemplifies a tube windingpattern which can result from winding a core without fins. As layer A iswound onto the core each row of tube within the layer nestles againstthe adjacent row of tube. Winding of rows within a layer continues untilthe layer is complete. A layer is completed when rows have been wound360 degrees around the perimeter of the winding disks. Subsequent layerscan be added over prior layers by winding additional rows of tube overthe prior layers. In the unfinned design, subsequent layers B, C . . . Nnestle in the groove created between the tubes of the prior layer. Asadditional layers are added, the spacing between the tubes of subsequentlayers increases relative to the spacing between the rows of the priorlayers, thereby, increasing the distance between the rows of tube in thesubsequent layer. Using this configuration, a winding core havingwinding disks with, for example, a diameter of 0.90 inches can be woundwith 40 rows of 0.040 inch diameter polyurethane tubing to a maximum ofeight layers. Using these parameters, a total of 300 cut tubes will bein the completed tube bundle. In the above example, the rows in thefirst layer are not biased against one another but, instead, are spacedevenly around the winding disk.

FIG. 4 shows an end view of a winding disk with fins in a one-layer findesign. The fins define primary notches 27 as the space between each twoconsecutive fins. The fins guide the tube into primary notches 27 as thetube is wound around the core. Thus, the fins represent an improvementover the design of FIG. 3 since the fins help locate the tube during thewinding process. Further, the fins allow winding on a winding corehaving a smaller inside diameter. The fins should be sufficiently thickso as to prevent stress fractures during molding of the core or breakageduring manufacture of the wound tube bundle. Typically, the thicknessshould be no less than 0.02 inches for application in cardioplegia heatexchangers. This minimum thickness also prevents moldability issues fromarising, like for example, the potential for warping and formation ofsink holes during cooling.

During winding of the one layer fin design, two rows of tube 30 aredeposited for each complete rotation of tube shuttle 26 around windingcore 10. The tube shuttle deposits the two rows of tube 30 onsubstantially diametrically opposite sides of the winding disk. Aftereach rotation of the tube shuttle around the core, the core is rotatedby an incrementing angle. The incrementing angle is the angulardisplacement of the core and determines the location where the next tworows of tube will be placed. For a winding core having a winding disk asin FIG. 4, the incrementing angle is chosen so that the core rotates adistance sufficient to allow the next winding cycle to deposit a tube inthe next notch or next desired multiple of notches. A layer around afinned winding core is completed after the winding apparatus hasdeposited tube 30 in all notches around the 360 degree perimeter of thewinding disks. Additional layers are then added by placing additionalrows in the notches over the rows in the prior layer. Thus, rows insubsequent layers butt against corresponding rows in the prior layersthe rows extending radially outward from the axis of the core.

Using the fin design of FIG. 4, a winding core having winding disks withan outer diameter of 1.6 inches, typical for cardioplegia heatexchangers, can be wound with 42 rows of 0.040 inch diameterpolyurethane tubing to a maximum of six layers. Using these parameters,a total of 252 cut tubes will be in the complete tube bundle.

FIG. 5 shows an end view of a winding disk having a two-layer findesign. The design utilizes the added thickness at the peripheral edgeof the fin to accommodate an additional secondary notch 28. Secondarynotches 28 have a larger inner diameter than primary notches 27 but thesame outer diameter. Therefore, secondary notches 28 will hold fewerlayers of tube than primary notches 27. Preferably, the thickness of thefins is no less than 0.02 inches for application in cardioplegia heatexchangers.

During winding of the two-layer fin design, initially only the primarynotches are wound. After the layer of tube in the primary notchesreaches the inner diameter of the secondary notches, the tube is woundinto both the primary notches and the secondary notches. At this point atransition layer is reached. The transition layer being the first layerin which tubes are wound into both the primary and secondary notches. Atthe transition layer the core rotating means halves the incrementingangle of the winding core. Halving the incrementing angle allows thewinding apparatus to place a row of tubing in both the primary and thesecondary notches. Winding continues until the layers reach the outerdiameter of the notches.

The two-layer fin design doubles the number and density of tubes whenthe tube is being wound into both the primary and the secondary notchesrelative to number and density of the one-layer fin design. Thereby, thetwo-layer fin design provides for more efficient utilization of space.The increased efficiency means more tubes are wound into less volume,which increases the thermal conductive contact surface area andtherefore increases the thermal efficiency of a heat exchange device orthe gas exchange efficiency, if the bundle is for use in an oxygenator.It also allows the device using the tube bundle to have a smallerpriming volume because the device's outside diameter can be smaller,important for most medical device applications.

Using the two-layer fin design, a winding core for a cardioplegia heatexchanger having winding disks with an outer notch diameter of 1.15inches, an inner primary notch diameter of 0.47 inches and using 0.040inch diameter polyurethane tubing can have eight layers. The primarynotches can be wound with 22 rows for the first four layers. Thefollowing four layers have 44 rows because of the combined primary andsecondary notches. Using these parameters, a total of 264 cut tubes willbe in the final tube bundle.

FIG. 6 shows an end view of the winding disk having a three-layer findesign. The three-layer fin design utilizes the remaining thickness atthe peripheral edge of the fin from the two-layer fin design of FIG. 5to accommodate an additional tertiary notch 29. Thereby, the three-layerfin design incorporates primary notches 27 and secondary notches 28 ofthe two-layer fin design and adds tertiary notches 29 between primarynotches 27 and secondary notches 28. Secondary notches 28 have an innerdiameter greater than primary notches 27 and tertiary notches 29 have aninner diameter greater than secondary notches 28. Therefore, secondarynotches 28 will hold fewer layers of tube than primary notches 27 andtertiary notches 29 will hold fewer layers of tube than secondarynotches 28. Preferably, the thickness of the fins is no less than 0.02inches for application in cardioplegia heat exchangers.

During winding the three-layer fin design tube is initially wound onlyin the primary notches. After the layers of tube in the primary notchesreach the inner diameter of the secondary notches the tube is wound intoboth the primary and the secondary notches. At this point a firsttransition layer is reached. The first transition layer is defined asthe first layer in which tubes are wound into both the primary andsecondary notches. At the first transition layer the core rotating meanshalves the incrementing angle of the winding core. Thereby, the windingapparatus places rows of tubing in both the primary and secondarynotches. Winding then continues until the layers of tube in the primaryand secondary notches reach the inner diameter of the tertiary notches.At this point a second transition layer is reached. The secondtransition layer being the first layer in which tubes are wound intoboth the primary, secondary and tertiary notches. At the secondtransition layer the core rotating means again halves the incrementingangle of the winding core. Thereby, the winding apparatus places tubingin the primary, secondary and tertiary notches. Winding then continuesuntil the layers of tubing reach the outer diameter of the notches. Thethree-layer fin design, like the two-layer fin design, doubles thenumber of rows and halves the incrementing angles at each transitionlayer. Thereby, the three-layer fin design allows more tubes to be woundinto a tighter volume, which again increases the thermal contact surfaceareas and therefore increases the thermal efficiency of the device whenthe bundle is used as a heat exchanger. Thus, the three-layer fin designresults in a device with even smaller priming volume than the single findesign or the double layer fin design.

Using the three-layer fin design, a winding core for a cardioplegia heatexchanger having winding disks with an outer diameter of 1.40 inches, aninner diameter of 0.54 inches and using 0.040 inch diameter polyurethanetubing can have ten layers. The primary notches can be wound with 16rows for the first four layers. The following four layers have 32 rowsbecause of the combined primary and secondary notches. The last twolayers have 64 rows because of the combined primary, secondary andtertiary notches. Using these parameters, a total of 352 cut tubes willbe in the final tube bundle.

The winding apparatus can additionally include a computer control,schematically represented in FIG. 7. The computer control regulates thecore rotating means and the shuttle rotating means. In the embodiment ofFIG. 7, the computer control includes a computer 31, shuttle stepperdrive 33, a shuttle stepper motor 34, a core stepper drive 33, and acore stepper motor 34. Tube bobbin 22 can also be provided with a bobbinstepper drive 37 and a bobbin stepper motor 38. Computer 31 is connectedto the stepper drives. The computer executes the winding software andissues commands to the stepper drives regarding when each motor is toactivate. The stepper drives are connected to the stepper motors. Thestepper drives then initiate the proper angular displacement of thestepper motors. Stepper motors are preferred because their rotation canbe precisely controlled, ensuring an accurate winding pattern at highspeeds. For example, if 22 degree incrementing angle is required laytube in subsequent notches on the core, as represented by φ in FIG. 6,then after one wind of the tube shuttle around the core, the core isrotated 22 degrees. The stepper motor, in this example, is designed suchthat 22 degrees will be achieved and held accurately. An appropriatesequence of instructions would be as follows:

1. a command to rotate 22 degrees is issued by the software in computer31 to core stepper drive 35;

2. core stepper drive 35 controls core stepper motor 76 to rotate 22degrees;

3. a command to rotate 360 degrees is issued by the software in computer31 to shuttle stepper drive 33; and

4. shuttle stepper drive 33 controls shuttle stepper motor 34 to rotate360 degrees.

The process then repeats until the winding is complete. The softwarewill control the timing, incrementing angles and number of passes aroundthe core in order to control the bundle's winding pattern. The softwarecan be implemented such that an external potentiometer 39 can controlthe rate of the winding process from its connection to computer 31. Thesoftware can also be written to allow the changing of variables, such asthe total number of winds around core 10 and the angular displacementfrom one row to the next. The software can also adjust the winding so asto recognize and adjust for transition layers for cores with finneddisks having secondary and tertiary notches. This will allow windingapparatus 1 to create bundles of many different sizes and patterns. In apreferred embodiment, computer 31 implements a bundle design with thefewest variable changes.

In operation of winding apparatus 1, tube 30 is routed from bobbin 22through tube shuttle 26 and is secured to winding core 10. Tube 30 ispreferably secured such that the end of tube 30 is not located betweenthe two winding disks. Tube 30 can be secured to winding core 10 usingan adhesive, tying or by other means well-known to those skilled in theart. Shuttle rotating means 28 rotates the shuttle around the windingdisks of winding core 10. Tube shuttle 26 thereby guides tube 30 aroundthe first winding disk 14 and the second winding disk 16 of winding core10. Each cycle is one complete revolution of shuttle 26 around windingcore 10. Each cycle results in two rows of tube being wound on windingcore 10. After each complete cycle around core 10, core rotating means20 rotates core 10 an appropriate incrementing angle such that theadjacent row can be wound onto the layer. The incrementing angle beingthe degree of rotation of core 10 required to align tube shuttle 26 withcore 10 such that the next rows wound will be adjacent to the prior row.When a finned winding core is used, core 10 is aligned and theincrementing angle chosen so as to maintain alignment between notches 19and the location at which tube 30 leaves tube shuttle 26. The cycle isgenerally repeated until the rows extend around the periphery of windingcore 10 completing the layer, although this may vary depending onwinding pattern. A second layer is then added on the outsidecircumference of the first layer and so on.

When a polyurethane tube is used for winding the tube can be tacky andself-adhere as it comes off the bobbin which can lead to inconsistenttension in the wound tube. Inconsistent tension creates slack in thetube line between the bobbin and winding core, which increases the riskof the tubing tearing, stretching out of shape, or snapping duringwinding. Thus, the winding apparatus can additionally include a meansfor applying substantially constant tension to the tube as the tube isdrawn from the bobbin. The tension means provides the further benefit ofremoving kinks in the lumen as the tube is removed from the bobbin. Thetension means includes at least one pulley around which tube 30 iswound. An embodiment of the tension means is shown in FIGS. 8A and 8B.FIG. 8A provides a top view and FIG. 8B provides a side view of anembodiment of the tension means. Tension means 80 of FIGS. 8A and 8Binclude a bobbin motor 27, a first pulley 42, a second pulley 44 and athird pulley 46. The tubing is wound from bobbin 22 around first pulley42, second pulley 44 and third pulley 46 and then through to the tubeshuttle, not shown. During subsequent winding, the rate of tube outputfrom the bobbin motor is slightly slower than the rate at which tube isbeing wound onto the core. The difference in rates generates a tensionon the tube. The pulleys are movably mounted and are biased by springsin the direction of first arrow 43, second arrow 45 and third arrow 47for first pulley 42, second pulley 44 and third pulley 46, respectively.The movement of the tension pulleys compensates for the sticking tubesby taking up the slack from the release of a tube stuck on the bobbin.During winding, the pulleys are displaced by the tension created bymotor 27 and the tube shuttle and confer a generally constant tensionover a distance proportional to the pulleys displacement. The amount ofdisplacement depends on the length and spring constant for each spring.Thereby, the tension pulleys maintain a substantially constant tensioneven when the tube sticks to the bobbin.

The winding pattern can vary depending on whether the fiber bundle isgoing to be used in a heat exchanger, dialyzer or oxygenator. In anembodiment used for a cardioplegia heat exchanger, the bundle is woundstraight across each winding disk of the core such that the tube iswound from a notch on one side of the core to a diametrically opposingnotch, as shown in FIG. 9A. The first row deposited is wind row n. Thewind rows in the pattern of FIG. 9A are deposited in diametricallyopposing notches. This results in the tube being angled around andbiased against winding pin 18. This represents the shortest distancefrom one side of the core to the other, and therefore minimizes theamount of tube thrown away after the winding disks are potted and cut.After row n is deposited the core is rotated by an incrementing anglecounter-clockwise such that the tube shuttle is aligned to wind tubeinto wind row n+1. As the cycles continue, the layers build up to form adome, shown in FIG. 13, around the winding pin at each end. At about thefourth to sixth layer, the dome reaches a size and angle where surfacecontact friction is no longer sufficient to keep the outer tube layersfrom slipping on the tube domes.

Typically, when more than four to six layers are required the windingpattern should be altered to avoid the tube's slipping, although, thelayer at which the pattern changes will depend on many variables,including the core design, tube size, tube material, tension applied, aswell as other variables recognized by those skilled in the art. Anexample of how the winding pattern can be altered is shown in FIG. 9B.For exemplary purposes, the winding pattern in FIG. 9B changes after thefourth layer. The pattern of FIG. 9B uses the winding pin to prevent thetube from slipping off of the dome. The tube is angled around thewinding pin thus biasing the tubing against the pin and preventing thetube from sliding off the dome. For illustrative purposes only, in FIG.9B the winding pattern change was made at the transition layer. In FIG.9B, the transition layer is the point where the tube count increasedfrom 22 rows per layer up to 44 rows per layer. The alteration inwinding shown in FIG. 9B rotates the tube counter-clockwise six notches(numbered 1 to 6) to prevent the tube from slipping off the dome. Thiswinding pattern results in twelve notches (numbered 1 to 6 and 1′ to 6′)without rows of tube when the subsequent layer is started and twelvenotches without tube upon completion of winding. Depending on theapplication for the tube bundle, it may be possible to keep the last fewnotches open on the last row, since a few tubes left out of the windwill not have a significant impact on the device's heat exchangeperformance. Alternatively, the winding pattern can be altered to athird configuration, as shown in FIG. 9C, to fill the notches leftwithout tubes after completing the pattern shown in FIG. 9B. The windingpattern of FIG. 9C rotates the core one increment less than 360 degreessuch that the tubing makes a 180 degree turn around the winding pin.Thus, adjacent rows are filled with rows of tubing until all the notcheshave a row of tube. This is exemplified in FIG. 9C as wind row n andwind row n+1 are deposited around the core wherein each wind rowdeposits two rows of tube.

In another embodiment of the winding apparatus shown in FIG. 10, thewinding apparatus utilizes two bobbins simultaneously. This embodimentof the winding apparatus includes: a winding core 110; a core rotatingmeans 120 rotating core 110 in the direction of arrow 121; a first tubebobbin 122 holding a first tube 130; a second tube bobbin 123 holding asecond tube 131; a tube shuttle 126 which simultaneously guides firsttube 130 and second tube 131 around core 110 in the direction of arrow129; and a shuttle rotating means 128 for rotating the shuttle aroundcore 110. First tube bobbin 122 and second tube bobbin 123 are rotatablymounted such that a length of tubing can be drawn off of the bobbins.First bobbin 122 and second bobbin 123 can be attached to a steppermotor and stepper driver such that the rotation of the bobbins iscoordinated by the computer control. First tube 130 and second tube 131may be composed of any biocompatible material flexible enough towithstand winding but the tubes are typically polyurethane for heatexchanger applications. First tube 130 and second tube 131 may have anoutside diameter of 0.01 to 0.10 inch and a wall thickness of 0.001 to0.050 but preferably has an outside diameter of 0.03 inches to 0.045inches and a wall thickness of 0.002 inches and 0.005 inches forcardioplegia heat exchanger applications. Tube shuttle 126 accepts firsttube 130 and second tube 131 from first bobbin 122 and second bobbin123, respectively. As tube shuttle 126 rotates around winding core 110first tube 130 and second tube 131 are draw from their respectivebobbins and wound end over end onto winding core 110, as shown in FIG.10. In this embodiment, the tube shuttle must align the tubing so as todistribute first tube 130 and second tube 131 in adjacent rows onwinding core 110. Furthermore, winding core 110 must have an even numberof notches. The winding apparatus pulls tubes from the two separatebobbins and winds it onto the core. Core rotating means 120incrementally rotates core 110 on an axis substantially parallel to andin the same plane as the tubing shruttle's rotational axis so the rowsof tube 130 and tube 131 are evenly distributed onto each layer woundaround core 110. In this embodiment, twice as much tube can be woundonto the core than with the embodiment shown in FIG. 1.

In another embodiment, not shown, a bobbin wound with two or more tubescan be used to wind multiple tubes simultaneously. The tubes must beextruded continuously and placed onto the bobbin such that the windingapparatus can draw the tubes off the bobbin at the same time. Thisembodiment requires a shuttle designed to distribute the two or moretubes onto a core. Further, the embodiment requires the addition of acomb to separate the tubes before winding onto the core.

After winding, the tube bundle is removed from the winding apparatus andthe bundle assembly is placed into a housing 50 shaped to accept thebundle. Housing 50 typically includes a fluid inlet 52 and a fluidoutlet 54 configured so as to allow a fluid to pass through housing 50and contact the outer surface of tubes 30. An exploded embodiment ofhousing 50 including a potted fiber bundle is shown in FIG. 11. Housing50 is designed to accept the wound bundle and function in the end use ofthe device. The wound bundle may be slightly oversized or undersized tofit within the housing as required by the application. In a preferredembodiment, the bundle is oversized by at least 0.003 inches to preventfluid shunting that could affect the device performance, particularly inmass transfer devices. Although for heat exchanger applications, suchover-sizing is not necessary because fluid shunting does notsignificantly affect the device's performance.

The wound bundle is potted at both ends within housing 50. The pottingmaterial is deposited within housing 50 defining a sealed fluid flowpath between fluid inlet 52, housing 50 and the tubes' outer surface,and fluid outlet 94. The potting material is preferably a thermosetpolyurethane compound or similar material. In defining the sealed fluidflow path, the potting material further provides a barrier between thetrans-lumenal space, through the lumen of the tubes, and the sealedfluid flow path, external to the tubes. In a heat exchanger for a bloodcardioplegia device, the potting material separates the water path,analogous to the sealed fluid flow path, from the blood path, analogousto the trans-lumenal space. Additionally, the potting material functionsto secure the bundle within the housing.

The wound bundle is preferably potted at both ends simultaneously usinga centrifuge, as shown in FIG. 12. Simultaneous potting reduces the timerequired to produce the fiber bundles because a single curing period canbe used instead of separate periods for the first and second ends of thebundle. Both ends are potted simultaneously by installing potting caps66 over each open end of the housing containing the fiber bundle.Potting caps 66 form a seal over the ends of housing 50 preventing thepotting material from leaking during curing. Potting caps 66 arepreferably made from or coated with a hydrophobic material such aspolypropylene, polyethylene or PTFE. The hydrophobic material preventsthe urethane potting material from adhering to the potting caps. Housing50 is mounted in a rotor 68 as shown in FIG. 12. The rotor is thenmounted in the centrifuge such that housing 50 spins around an axis Y soas to force potting material into end caps 66. In the embodiment of FIG.12, the potting material is supplied from a potting cup 69 whichutilizes centripetal force generated by the centrifuge to pull pottingmaterial out of cup 69 and into end caps 66 on housing 50. Thus, thepotting material is directed from the cup 69 into end caps 66 throughinlet 52 and outlet 54 of housing 50. Alternatively, the pottingmaterial can be directed from the cup 69 into end caps 66 through tubes,not shown, connecting potting cup 69 to end caps 66. Housing 50, thewound bundle, end caps 66 and potting cup 69 are centrifuged at a ratesufficient to force the potting materials to the ends of the housing andremove any entrapped bubbles. Typically, the force applied is between100 times and 220 times the force of gravity. Preferably, the centrifugeis maintained at a temperature above 25 degrees Celsius to expeditecuring. The centrifuge is run for between 15 to 60 minutes depending onthe time required for the urethane to set up enough for safe handling.This force ensures the urethane will penetrate the bundle completely,adhere to the surfaces of tubes 30, housing 50 and winding core 10, andprevent micro-bubbles from forming due to the off gassing while theurethane cures. After centrifugation the device is further cured at 40degrees Celsius for a minimum of 13 hours. After curing, potting caps 66are removed exposing the potted ends of the device.

Potted ends 71 are removed with a cross-cut 72 to expose the lumen ofthe tubes, as shown in FIGS. 13A and 13B. Prior to cutting, the entireassembly may be heated. The heating of the bundle softens the bundle tobetter facilitate cutting the ends. Cut 72 is made at each end of thedevice and cuts through the potting material (not shown), tube 30,cutting pad 15 and typically winding pin 18. If winding pin 18 iscomposed of an uncuttable material then pin 18 must be removed beforecutting. Cuts 72 are performed in such a manner that a uniform, flatsurface is formed on each end. Cuts 72 are made parallel to the topsurface plane of the device. Cuts 72 are made proximal to the creasesformed during the winding process. The creases are created at each endof the bundle where the tube bends around cutting pad 15. Therefore, itis desirable to make the cut below the crease in order to insure thatthe lumen of the tubes are not restricted. Typically, this results incuts 72 made about 0.033 inches above the top and bottom lip of thehousing holding the potted bundle. Cuts 72 are made with a two-sidedmicrotome blade or similar cutting technique. Usually a first rough cutis used to remove a large portion of the material, followed by two orthree cuts between 0.001 and 0.005 inches thick to obtain the final,desired surface finish. Cutting in this manner prevents a concavesurface from forming which can be undesirable because of poor flowdynamics and possible creation of stagnate areas that might provethrombogenic to the blood.

In a preferred embodiment, cutting pads 15, tubes and potting materialare composed of the same material. Typically, the material will bepolyurethane. Using the same material facilitates uniform deformationand shear resistance through the process of cutting. This ensures arelatively flat surface is generated, as opposed to the risk of bladeslippage created by cutting through materials of different hardness andthe waviness in the cut surface which can result. A typical uniformhardness such as shore 65 D will insure a flat surface is made duringthe cutting process.

To use a completed fiber bundle in a heat exchanger, for example, endcaps are placed over the cut ends of the bundle within the housing. Thefirst end cap having a blood inlet and the second end cap having a bloodoutlet. The end caps are configured such that the lumen of tubes is incommunication with the blood inlet at the first end and the blood outletat the second end. In operation, blood entering the blood inlet isdirected through the lumen of the tubes exiting the device through theblood outlet. Simultaneously, a heat exchange fluid is directed throughthe water inlet contacting the outer surface of the tubes and exitingthrough the water outlet. Thereby, heat is exchanged between the bloodand the heat exchange medium through the tubing wall of the tubes in thebundle.

The bundle formed in the above-described embodiments is suitable for useas a heat exchanger in a blood cardioplegia circuit and the dimensions,tubing, surface area, and other particulars are suitable therefore. Asmentioned previously, the method and winding device of the presentinvention can also be used to make tube bundles for applications such asblood oxygenators or hemoconcentrators that utilize a mass transferdevice.

If the instant method and apparatus is used to make a blood oxygenator,more tubing surface area is necessary than in the embodiments for use asa heat exchanger. Typically, blood oxygenator mass transfer devices canhave as little as 1.8 square meters of surface area. The tubes used inoxygenators typically have a diameter of between 0.018 to 0.022 inches.The tubes typically have a nominal wall thickness of 0.03 to 0.20micrometers and a porosity of about 40%. Given these dimensions, anoxygenator bundle with a surface area of 1.8 square meters would includeabout 14,800 fibers if the bundle were about six inches in length. Thisresults in a bundle diameter of approximately two to five inches,depending on the notch design chosen. The smaller diameter of thisdesign translates into a lower priming volume and therefore lesshemodilution. Typically, in such applications, the path of blood flowwould be exterior to the hollow fibers or tubes making up the bundle.

Similar specifications can be used for polymer based hemoconcentratorsand dialyzers. The tube used for these applications is typically apolymer which may be a cellulose based polymer or a synthetic polymer.The cellulose tube material used can include cuprammonium rayon, viscoserayon and cellulose acetate. The synthetic tube material used caninclude polyvinyl alcohol, ethylene vinyl alcohol, polysulfone,polypropylene or polymethyl-methacrylate. The tube is usually 200 μm to300 μm in diameter with a wall thickness of 5 μm to 20 μm. The overallconfiguration for hemoconcentrators and dialyzers are the generally thesame as described above for heat exchangers. Specifically,hemoconcentrators and dialyzers can have a similar geometries, similarnumber of tubes and similar surface areas. Typically, the blood flowwithin the hemoconcentrator or dialyzer is through the tubes' lumen anddialysis solution or saline runs over the outer surface of the tubes.

What is claimed is:
 1. An apparatus for manufacturing a wound tubebundle for use in medical device applications, comprising: a tube; atube shuttle shaped to receive and distribute the tube; a winding corehaving a body, a first winding disk and a second winding disk, the firstwinding disk attached to a first end of the body and the second windingdisk attached to a second end of the body, wherein the first windingdisk and the second winding disk are shaped to accept tube from the tubeshuttle; a shuttle driver for rotating the tube shuttle about a shuttleaxis in a circular winding motion; and a core driver for incrementallyrotating the winding core about a longitudinal axis of the core, thelongitudinal axis being substantially perpendicular to and substantiallyintersecting the shuttle axis, the shuttle driver and core driver beingconfigured to rotate the shuttle and the winding core in a manner thatdistributes the tube on the winding core in layers, each layer having aplurality of rows, each row being substantially parallel to the otherrows and substantially parallel to the longitudinal axis of the core. 2.An apparatus, as in claim 1, wherein the winding core further comprisesa first cutting pad attached opposite the body on the first winding diskand a second cutting pad attached opposite the body on the secondwinding disk.
 3. An apparatus, as in claim 1, further comprising a tubebobbin for holding a length of the tube and for dispensing the tube tothe tube shuttle.
 4. An apparatus, as in claim 1, wherein the windingcore further comprises a plurality of fins extending radially from aperipheral edge of the first and second winding disks, the plurality offins defining a plurality of primary notches configured such that tubewound onto the winding core is positioned within the primary notches. 5.An apparatus, as in claim 4, wherein the plurality of fins furtherdefine a plurality of secondary notches shaped to receive tube from thetube shuttle, the primary and secondary notches each having a length asmeasured from the peripheral edge towards the central axis, the lengthof the primary notches being greater than the length of the secondarynotches.
 6. An apparatus, as in claim 5, wherein the plurality of finsfurther define a plurality of tertiary notches shaped to receive tubefrom the tube shuttle, the tertiary notches having a length as measuredfrom the peripheral edge towards the central axis, the length of thetertiary notches being less than the length of the secondary notches. 7.An apparatus, as in claim 1, wherein the core driver is configured toincrementally rotate the winding core one increment after each fullrotation of the tube shuttle around the winding core.
 8. An apparatus,as in claim 1, further comprising a computer control wherein thecomputer control is configured to regulate at least one of the rate,degree and timing of the rotation of the tube shuttle and the windingcore.
 9. An apparatus, as in claim 1, further comprising a bobbin driverfor incrementally rotating the tube bobbin.
 10. An apparatus, as inclaim 9, further comprising a computer control wherein the computercontrol regulates at least one of the rate, degree and timing of therotation of the tube bobbin.
 11. An apparatus, as in claim 1, furthercomprising a means for providing a constant tension to the tube as thetube is unwound from the bobbin.
 12. The apparatus of claim 1 furthercomprising a winding pin extending co-axially from the winding core. 13.The apparatus of claim 12 wherein the winding pin is shaped to securethe winding core to the winding apparatus.
 14. The apparatus of claim 1wherein the winding core further comprises a first cutting pad attachedto the first winding disk and a second cutting pad attached to thesecond winding disk.